1. Field of the Invention
The present invention relates to a system for deicing aircraft. In the preferred embodiment, the invention is directed to a mobile, one-step deicing system which utilizes a preselected ratio of heated water and heated Type II deicing fluid, thereby increasing the time period during which the aircraft is protected.
2. Description of Prior Art
In many circumstances, aircraft are subject to severe winter conditions during which ice and snow can accumulate on the aircraft and the control surfaces of the aircraft. The accumulation of snow and ice on aircraft presents a serious safety hazard, and it is therefore necessary to take all appropriate steps to ensure that an aircraft is protected against dangerous icing conditions.
One of the conventional methods of deicing aircraft is to apply a mixture of glycol (Type I) fluid and water at a 1:1 ratio, commonly known as a 50/50 glycol mix. This mixture is typically heated to approximately 180.degree. to 205.degree. F. and sprayed on the aircraft control surfaces at a rate of approximately 60 gallons per minute at a pressure of approximately 80 psi. Such a 50/50 mixture of water and glycol does a fairly good job of removing frost, ice, or snow from the aircraft, and during light winter precipitation and moderate temperatures will provide a short holdover time. Examples of apparatus and methods typically used to provide such water and glycol deicing are illustrated, by means of example only, in U.S. Pat. Nos. 3,243,123 to Inqhram et al; 4,073,437 to Thorton-Trumc; 4,032,090 to Thorton-Trumo; and 4,333,607 to Mueller et al. As disclosed in certain of the above patents, the deicing systems presently available often are included as part of a truck which can be driven to the aircraft.
In severe weather conditions, a 50/50 or similar mixture of water and glycol does not provide a sufficient protective coating or holdover time. In an attempt to solve this problem, some deicing vehicles have an extra tank of 100% glycol. After the aircraft is deiced by the heated water and glycol mixture in the first step, cold concentrated 100% glycol is then sprayed on the control surfaces in a cold state to provide an antiicing effect. This antiicing step with 100 percent glycol generally adds to the holdover time to some degree, but still provides only modest protection.
A second type of antiicing fluid, known as A.E.A. Type II fluid, has been used in Europe and in limited application in the United States. Type II fluid is a thixotropic, highly viscous fluid which provides longer holdover protection. However, Type II fluid is an extremely shear sensitive and temperature sensitive fluid which easily degenerates. It is also difficult to mix Type II fluids with other fluids, without degenerating the Type II fluid. Because of its unstable nature, it has been difficult to apply Type II fluid in a commercially acceptable and economic manner.
Type II fluid has been used in Europe with moderate success, but the application process is time consuming and inefficient. Generally, the Type II fluid is first pre-mixed with water in a special vat located in a hanger or similar building. The mixture is then heated in the vat, and, when heated, transferred to a tank in a mobile truck. The truck then is driven to the aircraft, and the preheated mixture is finally applied to the aircraft.
Type II fluid has been used only on a limited basis in the U.S. To applicant's knowledge, the Type II fluid has been used in the U.S. only in a two-step process. In the first step, the aircraft is deiced through a hot water or glycol-water mix to remove all ice and snow from the aircraft. Then, a cold Type II fluid is coated onto the airplane.
The past processes and apparatus for using Type II fluid, therefore, have been expensive and time consuming. As a result, the use of Type II fluids, particularly in the U.S., is not well accepted.